Field of the Invention
The invention relates to an installation for processing wafers.
These types of installations contain a number of processing units, with which various fabricating steps for processing wafers are carried out. The fabricating steps include etching processes, wet chemical processes, diffusion processes, and various purifying techniques such as CMP (Chemical Mechanical Polishing). One or more processing units are provided for each of these fabricating steps. In addition, measuring units are provided, wherein the quality of the wafer processing can be checked. These measuring units are expediently utilized to check all essential fabricating steps which are executed in the processing units.
The overall fabrication process is subject to stringent purity requirements, for which reason the processing units and measuring units are disposed in a clean room or a system of clean rooms.
The wafers are supplied to the individual processing units and measuring units in a predetermined batch size by way of a transport system. To accomplish this, the wafers are transported in transport containers, which are implemented in the form of cassettes, for instance, whereby the transport containers each accept an equal number of wafers. The wafers are also delivered out by way of the transport system after being processed in the fabrication and measuring units, whereby they are borne in the same transport containers. Typically, 25 wafers are combined into one batch in each transport container.
The transport system includes a conveyor system, which is constructed in the form of roll conveyors, for instance. The transport system additionally includes a storage system with a plurality of stores for storing transport containers with wafers.
In prior art wafer processing installations, a batch of wafers is combined in a transport container and fed through all fabrication and measuring units of the installation via the transport system. The batch remains attached to the respective transport container. This means that wafers from different batches are not mixed.
To process the wafers, a respective transport container containing a batch is fed to a processing unit or measuring unit via a loading and unloading station. After the wafers are processed in the fabrication or measuring unit, the batch is output to the transport system again via the loading and unloading station in the same transport container.
The transport containers with the wafers are successively fed to the individual fabrication and measuring units according to the order of the individual fabrication and measuring processes. This is problematic, because the individual fabrication and measuring units have different processing capacities. This is particularly ascribable to the fact that in some fabrication and measuring units a number of wafers can be processed in parallel, while in other fabrication and measuring units only individual wafers can be processed. For example, in furnace processes a number of wafers can be supplied to the furnace of a processing unit simultaneously. In measuring units, on the other hand, wherein an optical inspection is performed, the wafers are processed individually.
In order to guarantee an optimally high capacity utilization of the apparatus in spite of this problem, an optimally high number of transport containers with wafers are output to the transport system. The disadvantage of this is that a substantial stock of wafers is located in the apparatus. But such large material stocks in the apparatus are extremely cost-intensive. In addition, because such a large number of transport containers cannot be fed through the apparatus continuously, it is necessary to provide a plurality of stores for temporarily storing the transport containers.
Stores such as these are typically constructed as stockers. A stocker consists of a storage system wherein the wafers are stored under clean-room conditions. Stockers such as these are extremely cost-intensive owing to the large constructional outlay. Furthermore, stockers require a substantial amount of space in the clean room, which raises the cost of the installation still further.
These measures notwithstanding, owing to the different processing capacities it is impossible to prevent substantial wait times and associated downtimes in individual fabrication and measuring units. This, of course, leads to long throughput times of the wafers through the apparatus. Typical throughput times for wafer processing installations are in the range of 40 to 60 days.
U.S. Pat. No. 5,083,364 and German published patent application DE 37 35 449 A1 disclose a fabrication installation for wafers which is built from several interchangeable transport modules, processing modules, and check modules. Each processing module includes at least one processing station, one deposit and one handling device.
The wafers are sent in via the transport system in a first cassette. The handling device removes the wafers from the first cassette and feeds them to the processing stations and deposits. In the check module, unusable wafers are captured and potentially collected in a second cassette. The second cassette can serve for the temporary storage of the unusable wafers. Alternatively, the unusable wafers are channeled out of the check module. The flawless wafers are collected in cassettes and output on the transport module.
U.S. Pat. No. 5,803,932 describes a processing installation for processing wafers. That processing installation includes a loading/unloading section, a processing section and an interface section. In addition, a transport device and at least two waiting sections are provided.
The transport device is located between the loading/unloading section and the interface section. A number of processing units, which form processing sections, are disposed on either side of the transport device.
The wafers are transported on the transport device either in the direction of the loading/unloading section or in the direction of the interface section.
U.S. Pat. Nos. 6,050,768 and 6,129,496 (see German patent application DE 198 16 151 A1) relate to a control method for an automatic transporter of a semiconductor wafer cassette transport device. The transporter transports a semiconductor wafer cassette to an inlet port of a storage device under the control of a host computer.
Japanese patent application JP 08268512 A relates to a storage unit for storing substrates. The storage unit includes a sorting unit with the aid of which the substrates are automatically sorted and sent in and out of the storage unit in cassettes.
German patent application DE 198 26 314 A1 teaches a test device for automatically testing integrated circuits (IC). To carry out the tests, a plurality of testing heads are provided at a test table. A transport device for transporting individual ICs is provided at the test table. The transport device includes arms that are movable on rails and that include a gripper head for picking up the ICs.
It is accordingly an object of the invention to provide a wafer processing installation, which overcomes the abovementioned disadvantages of the heretofore-known devices and methods of this general type and which achieves an optimally short throughput time of the wafers through the installation given an optimally high utilization of the capacity of the fabrication and measuring units.
With the foregoing and other objects in view there is provided, in accordance with the invention, an installation for processing wafers, comprising:
a configuration of processing units (e.g., fabrication units for executing individual fabricating steps and measuring units for checking the results of the fabricating steps) disposed in one of more clean rooms;
a transport system interconnecting the processing units for transporting wafers to and from the processing units, wherein the wafers are combined into variable batch quantities, adapted to capacities of at least one of the processing units and the transport system, in transport batches for transport on the transport system and processing batches for processing in the processing units;
computing units connected to the processing units and the transport system, and a fabrication control connected to the computing units for selectively combining a plurality of wafers into a batch;
the fabrication control transmitting a control command to a computing unit of the transport system for compiling a transport batch, the control command including information regarding a size of the batch and a processing unit constituting a destination for the transport batch;
wherein, upon reaching the destination, the transport batch is dismantled in the respective the processing unit, and the wafers of the batch are converted into a processing batch;
wherein, after being processed in the processing unit, the processing batch is dismantled and converted into at least one transport batch; and
the fabrication control transmitting a control command to a computing unit of the processing unit for compiling the at least one transport batch, and the control command containing an identification, a batch size, and a destination selected from the group consisting of a fabrication unit, a measuring unit, and a store of a storage system of the installation.
The wafers, according to the invention, are combined into variable batches sizes, which are adapted to the capacities of the processing units, measuring units and/or transport system. The wafers are combined into transport batches for transport on the transport system and processing batches for processing in the fabrication or measuring units.
The basic idea of the invention is to do away with the attachment of the wafer to a particular batch of a strictly prescribed size.
The transport of the wafers by way of the transport system is accomplished in variable batch sizes, whereby the individual batch sizes are adapted to the processing capacity and the instantaneous level of capacity utilization of a fabrication or measuring unit to which the wafers are being fed.
In the individual fabrication and measuring units, the wafer batches which are sent in by the transport system are divided up and combined into new batch quantities according to the demand and capacity of the fabrication or measuring unit, and processed at the same time in a new batch. If the wafers are already being sent in by way of the transport system in the batch size which is demanded by the respective fabrication or measuring unit, the dismantling of the old batch and compiling of a new batch can be omitted.
After a batch is processed in a fabrication or measuring unit, this batch is dismantled again, and new batches of wafers are created therefrom, as needed, which are then fed to the transport system. The individual batches are then fed to subsequent fabrication or measuring units according to the processing order in the overall process.
The batches can include up to 300 wafers, depending on the individual fabrication and measuring units. Likewise, very small batches can also be provided, including even a batch of one. Accordingly, single-wafer processing is also possible in the inventive apparatus. Marks are then made on the wafers, with the aid of which the wafers are identifiable by suitable identification apparatuses.
By adapting the batch sizes to the capacities of the individual fabrication and measuring units, the throughputs in the individual fabrication and measuring units can be effectively balanced. The wait times and downtimes of the individual fabrication and measuring units are thereby substantially shortened, and a short throughput time of the wafers through the apparatus is achieved. Another consequence of this is that only a small number of wafers are still stored in the temporary store, since few overcapacities, if any, occur in the transport system by virtue of the demand-sensitive supplying of wafers to the fabrication and measuring units. This makes it possible to forgo cost-intensive stores and to substantially reduce the stock of wafers in the apparatus.
In accordance with an added feature of the invention, the transport batches and processing batches are of different sizes.
In accordance with an additional feature of the invention, a batch quantity includes at least one wafer.
In accordance with another feature of the invention, markers are disposed on the wafers, for individual identification of the wafers.
In accordance with a further feature of the invention, a plurality of transport containers are provided, each accommodating a respective batch. The batches are preferably identified with an identifying marker.
In accordance with again an added feature of the invention, the transport system includes a conveyor system and a storage system with at least one store, and each conveyor system and storage system includes at least one the computing unit. There are also provided a plurality of reading devices for reading the markers on the wafers connected to the computing units.
In accordance with again an additional feature of the invention, the control command contains a transport time for feeding the transport batch to the destination.
In accordance with again another feature of the invention, in order to dismantle a transport batch, a computing unit of a processing unit constituting the destination transfers a control command to the fabrication control, whereupon the identifying marker of the transport batch is erased from the fabrication control. Preferably, the identifying marker of the processing batch generated in the processing unit is read into the computing unit of the processing unit by the fabrication control.
In accordance with again a further feature of the invention, in order to dismantle a processing batch, the computing unit of the respective processing unit transfers a control command to the fabrication control, whereupon the fabrication control transfers to the computing unit a reply with a control command for compiling at least one transport batch.
In accordance with a concomitant feature of the invention, upon receiving the control command for dismantling the processing batch sent by the computing unit of the processing unit, the identifying marker of the processing batch is erased from the fabrication control.
In the case in which a central control, i.e., a fabrication control is provided, the transport system and the individual fabrication and measuring units include computing units, which are connected to the fabrication control. The compiling and dismantling of the batches are then accomplished by a communication of control commands from the fabrication control to the computing units, with information being fed back in the reverse direction from the computing units to the fabrication control by way of the transport system and the fabrication and measuring units.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an installation for processing wafers, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.